Tertiary Mg/MgCl₂/AlCl₃ Inorganic Mg²⁺ Electrolytes with Unprecedented Electrochemical Performance for Reversible Mg Deposition

Because of the high reactivity and sensitivity of Mg 2+ electrolytes in organic solvents, developing facile methods of preparing high-performance Mg 2+ electrolytes is still challenging and thus impedes the development of Mg batteries. In this study, a convenient method involving tertiary reactants, Mg powder, MgCl 2, and AlCl 3, was reported to prepare all-inorganic Mg 2+ electrolytes (termed MMAC electrolytes) in ethereal solvents. These MMAC electrolytes exhibited unprecedented performance for reversible Mg deposition, Coulombic efficiencies at 90–100%, overpotential of 125–215 mV, and anodic stability up to 3.5–3.8 V (vs Mg). A comprehensive fundamental study of the MMAC electrolytes showed that the electron transfer and mass transport kinetics during Mg deposition and stripping were affected by solvent, working electrode, and the composition of the electrolytes. In brief, these tertiary MMAC electrolytes represent the most facile and reliable inorganic Mg electrolytes known to date.